Photographic silver halide transfer product and process



Dec. 28, 1954 LAND 2,698,236

PHOTOGRAPHIC) SILVER HALIDE TRANSFER PRODUCT AND PROCESS Filed May 27,1954 loci \1' 5.1 Processing Agent Supporf [6 K 120 SilverPrecipifoi'ing Layer FIG. I

/Prin+ Receiving Elemcnf FIG. 2

(Abrasion Rcsisiumi Coui'ing Sil vcr Prccipifaiing Layer FIG. 3

INV NTOR ma ATTORNEYS Un wd. S tes- 13mm 0.

Edwin H. Land, Cambridge, Mass, assignor to Polaroid Corporation,Cambridge, Mass., a corporation of Delaware 1 Application May 27, 1954,Serial No. 432,813

34 Claims. (Cl. 95--8) This invention relates to photographic products.and processes and more particularly to transfer processes wherein alatent image in a silver halide emulsion is developed and wherein asoluble silver complex obtained by reaction with the undeveloped silverhalide of said emulsion is transferred from said emulsion and the silverthereof is precipitated in another layer to form a positive print, andto products useful as print-receiving elements in said processes.

This application is a continuation-in-part of my copending applicationSerial No. 164,908, filed' May 29, 1950, whlch, in turn, is acontinuation-in-part of my copending application Serial No. 727,385,filed February 8, 1947, for Photographic Product and Process.

One object of the present invention is to provide a transfer process ofthe foregoing type and products for use in said process whereby thereareproduced positive prints of good quality and stability from silverhalide emulsions of high speed.

Another object of the present invention isto provide an improved productparticularly useful in the foregoing transfer processes as theprint-receiving element, said product comprising a novel silverprecipitating layer adjacent one surface thereof, which layer serves toeffect a controlled precipitation of the silver from the soluble silvercomplex and also acts to receive and suitably aggregate the precipitatedsilver to producedense positive images of excellent pictorial quality.

Another object of the present invention is to provide a print-receivingelement which has a novel silver precipitating layer comprising a heavymetal sulfide for selenide as its precipitating agent andwhich alsocontains suitable salts for preventing diffusion or wandering-of thesilver precipitating agent from its originalloeus in said layer.

Still another object of the present invention is to provide a novelprint-receiving element which also includes materials for greatlyimproving the stability of the positive silver print formed in saidelement.

Other objects of the invention will in part be obvious and will in partappear hereinafter.

The invention accordingly comprises the several steps and relation andorder of one or more of such steps with respect to each of the others,and the product possessing the features, properties and the relation ofelements which are exemplified .in the following detailed disclosure,and the scope of the application-of which will be indicated intheclaims. M '1 For a fuller understanding of the nature and objects of theinvention, reference should be had to the following detailed descriptiontaken in connection-with the .accompanying drawing wherein:

Figure l is a diagrammatic, enlarged sectional view illustrating theassociation of elements during one stage of the performance of atransfer process and showing asone of the elements an embodiment of thenovel product of the present invention, the thicknesses of the variousmaterials being exaggerated;

Fig. 2 is a perspective view, with parts broken away, of one form ofprint-receiving element upon which containers of the processing agentare so positioned as to be capable of distributing their contentsbetween the surfaceof the print-receiving element and a photosensitiveelement; and

the print-receiving element of the invention.

The present invention comprehends improved processes,

, of zinc, cadmium and lead.

In general, the sulfides and selenides of the alkali metals and productsof the type whereby a positive print is obtained in a single step bysuitably treating a silver halide emulsion containing a latent imagewith a uniformly applied layer of processing liquid. Preferably, theprocessing liquid is in a viscous condition and .is spread in a liquidfilm between the photosensitive element comprising the silver halideemulsion and a print-receiving element comprising a suitable silverprecipitating layer. The liquid develops the latent image in theemulsion and forms a soluble silver complex, e. g., a thiosulfate or athiocyanate, with undeveloped silver halide. This soluble silver complexis at least in part transported in the direction'of the print-receivingelement and the silver thereof is largely precipitated in the silverprecipitating layer of said element to form a positive image in silver.

It has been proposed to use in the formation of the silver transferprints by the foregoing process certain compounds and elements whosepresence during the'process has a desirable effect on the amount andcharacter of thesilver precipitated during image formation. For thispurpose, such materials as, for example, the metallic sulfides andselenides, thiooxalates, and thioacetamides have been disclosed in myLetters Patent No. 2,647,056, issued July 28, 1953. Other precipitatingagents have been proposed such, for example, as colloidal silver.

According to the present invention, the precipitation and aggregation ofsilver obtained by using the silver precipitating agents, including theabove-mentioned materials, is very greatly improved by providing in theprint-receiving element as a dispersing medium for said agents a layerof silica such, for example, as is formed from the hydrated colloidalsilica dispersion available under the trade name Ludox or the silicaaerogel avail-. able under the trade name Santocel C.

The novel silver precipitating layer including the'silica and the silverprecipitating agent is preferably applied-to a suitable support, forexample by being coated on the support in the form of a suspension whichcontains a substantially greater amount of the silica than of theprecipitating agent. The support may be formed 'of materials such aspaper, regenerated cellulose, polyvinyl alcohol, cellulose ethers suchas methyl cellulose, ethyl cellulose, or their derivatives, such assodium carboxymethyl cellulose and hydroxyethyl cellulose, and othernatural and synthetic gums and resins which will form continuous filmsand which are relatively stable, meehani cally, in the presence of waterand alkali.

Although the present invention comprehends, as silver precipitatingagents, such materials as certain of the colloidal metals, e. g.,silver, most satisfactory results: are obtained by using the relativelywater-insoluble metallic sulfides and selenides. Examples of silverprecipitating agents of this preferred type are the so-called heavymetal sulfides of zinc, chromium, gallium, iro'n, cadmium, cobalt,nickel, lead, antimony, bismuth, silver, cerium, arsenic, copper andrhodium and the selenides of lead, zinc, antimony and nickel. For bestresults, it is preferable to employ the sulfides whose solubilityproducts in an aqueous medium at approximately 20 C;

vary between 10* and 10- and specifically the salts and alkali earthmetals such as sodium, potassium, cesium,

calcium, barium, and magnesium are too soluble to give'. optimumpictorial quality, although the PIOVISlOH'Of'a" silica layer asavehicle'for such precipitating agents greatly improves'the resultsobtained with said agents;

The concentration of the silica in the silver precipitating" layer ispreferably high enough to give a macroscopically silver precipitatingagent is present in a very small amount. It has been determined thatfurther improvements in image quality are obtained when using one ormore of the heavy metal sulfides and selenides as silver precipitating:agents if the sulfide or selenide 1ons of the crystals are preventedfrom wandering or diffusing during prec1p1ta-. tion from their originalloci in the preclpltatmg layer. In the following discussion of this andother phenomena involving the action of the sulfide and selenide salts,-reference will be made to the sulfides alone, but 1t 18 tov PatentedDec. 28,, .1954

be understood that wherever such reference is made, the same, unlessotherwise stated, is generally applicable to the selenides.

To prevent the diffusion and wandering of the sulfide ions, there ispreferably included in the silver precipitat inglayer or closelyadjacent thereto at least one metallic salt which is substantially moresoluble in the processing agent thanthe heavy metal sulfide used as thesilver precipitating agent and which is irreducible in the processingagent, said more soluble salt having, as its cation, a meta whose ionsform sulfides which are difiicultly soluble in the processing agent andwhich give up their sulfide ions to silver by displacement. Accordingly,when such sulfide ions are present, the metal ions of the more solublesalt'have the effect of immediately precipitating the sulfide. ions fromsolution.

The special function of this combination of a sulfide, a more solublemetallic salt and a silica will be better understood by considering thenew sequence of reactions which takes place when aprint-receivingelement so constituted is used in a silver halidetransfer process involving a silver halide developer and a silver halidesolvent, such as sodium thiosulfate. This sequence of reactions isperhaps best described in my article One-Step Photography appearing inSection A of the January, 1950 issue of the Photographic Journal(British) as follows:

First: The silver ion in the silver halide of the negative is protectedby its environment in the crystalline halidefrom being reduced, but itprefers the thiosulphate ion as an associate, so the silver halidedissolves.

Second: The silver ionis now protected from reduction by thethiosulphate complex, but it prefers the sulphide ion as an associate,so that silver sulphide is formed and would be precipitated as such ifit were not for the fact that the sulphide ion-in'spite of theinsolubility of the crystalline compounddoes not protect the silver ionfrom reduction. Thus, the silver ion has been safely pried loose andtransported to a new site where it becomes silver, and the transportingions are free to carry on their cyclic efforts- Is this then the end?Actually, it is the beginning, for while we have learned how to extractthe silver ions fromthe negative and to precipitate them as reducedsilver rapidly, we are just beginning to consider how to build up anacceptable positive from the point of view of appearance (and of coursewe have not yet considered our prob,- lems of stabilizing an imageresident in this complicated reagent).

What we find when we use sulphide ions to release silver ions from thethiosulphate complex is the'following gamut of problems:

(1). Sulphide ions in solution provide so many points of initiation thatan enormous numberof grains start growing. betoo dense. If they remainsmall, the picture will be bright. yellow (you will recall that, thecolour of'silver colloids depends on the particle size).

(2). There is a tendency for the grains in the shadows, opposite. theunexposed portions of the negative, where much silver is available, togrow larger than the grains in the medium tones, where the availablesilver concentration'is low, producing an unpleasant combination of blueshadows and yellow high lights.

(3). Some of the sulphide ions migrate into the negatlve, dropping theconcentration in the positive and fogging the negative.

"Thus, having determined how to extract silver ions from the.appropriate part of the negative, and how to. reduce them to silveratoms, we are still confronted with the problem of how to build theseatoms into arrays of the correct diameter for absorbing-visible light.We must also achieve adequate constancy in diameter so that highlightand shadow are the same hue.

Since the. sulphide'ions are the last factor in the chain of eventsleading to silver precipitation, let us consider how these might bearranged to influence the arrayof silveratoms'. Let us suppose that wecan arrange the sulphide ions in clusters, allowing the diameter of the.cluster to be that of the mass of silver we seek to build. The actualmass of sulphide ions might then be very low 1ndeed-s ubject to onevital proviso, namely that as-the sulphide ons perform their cyclicfunction, they are retained within the diameter that we have chosenforthe cluster. If we can meet this condition, then we can cause the silveratoms to fill in the volume of the cluster to make- If these becomelarge the whole picture will process with quite good resolving power.

our mass of silver of the required density and size. To do all this wemust extend the chain of circumstances that we have been following fromthe negative outward.

By forming colloidal crystals of heavy metal sulphides which are notreducible generally in or soluble in the developer, and by aggregatingthese colloidal crystals into galaxies of our chosen diameter, we canarrange the sulphide ions as we desire them. In this new environment thesulphide ion is bound in place until the silver thiosulphate complextouches it. The silver ion-just as it once left the halide ion for thecomplex-now leaves the complex ion to form the sulphide. The sulphidesimilarly leaves the metal ion for association with the silver. Then thesilver is reducedbut mark you, reduced in situ reduced at the pointwhere we originally deposited the colloidal particle of metal sulphide.We have started well in building up our mass of silver. But the sulphideion, now free, is not likely to encounter the metal ion to which it wasbound if it escapes from the galaxy and wanders off. We are in danger ofreverting to some extent to the problems that occured with the solublesulphide. This danger can be avoided by introducing into the positivesheet at the time of manufacture a relatively high concentration of asoluble salt of the same metal that we used in the colloidal sulphide(or indeed of some other metal, providing that its sulphide is moresoluble than silver sulphide and is not reducible in, or soluble in, thedeveloper). After the viscous developer is spread, the metal salt in thepositive sheet dissolves, and be cause of the relatively highconcentration of these metal ions, the sulphide. that is, freed at itsoriginal site by the reduction of the silver is at once captured beforeit can leave that site, and reprecipitated as the sulphide of the metal.In his way, the diameter of the galaxy is maintained. in spite of thecyclic use of the sulphide ions. The silver ions are reduced to silverover the same area that wechose for the original galaxy, and thediameter of the mass of silver is such that our image is the colour wepredetermined when we prepared the metal-sulphide galaxies. Oneremarkableaspect of pictures made in this way is, that thev silverin thepositive has very high covering power.in theorder of fivetimes that ofthe silver in the negative. Consequently a good positive can be madefrom a layer of silver. halide that is many times thinner than isordinarily required for a negative. While full thickness negatives canbe used for making this new kind of positive, it is impressive to seehow thin a layer of negative material suflices. The negative image, whensuch a thin emulsion is used, is only just visible, yet the positivederived from the same amount of silver is rich and brilliant; Thus, wesee that this process provides a type of intensification. Furthermore,since only the surface of the negative'is involved, there is gain inspeed, and a gain in sharpness both in exposing and printing. Indeedthe. migration distance for the silver ions going from the negativesheet to the positive image can be extremely small. We have, seen thatthese ions come from very near the surface of the negative, and we can,if we choose, precipitate the silver in the viscous positive layer atthe surface of the negative. Thus, the combination of minimized lightscattering in the negative, the short migration distance-for the silverions, and the prompt precipitation of them when they reach the positive,results in :1 Furthermore, the pictures are by all ordinary standardsgrainless, bccause-of the way in which the silver is deposited andaggregated. (Underlined words added or modified.) v

The silver precipitating agent is dispersed in silica which aids theformation of the aforementioned galaxies, and it is evident, from theforegoing, that the presence of the more soluble salt, which providesthe cations for capturing the free sulfide ions, has the effect ofmaintaining this desirable aggregation of the sulfide ions during thesilver precipitation. These more soluble or ioncapturing salts may bethe soluble salts of any of the following metals: cadmium, cerium(ous),cobalt(ous), iron, lead, nickel, manganese, thorium and tin.Satisfactory soluble and stable salts of the above metals may be found,for example, among the following groups of salts: the acetates, thenitrates, the borates, the chlorides, the sulfates, the hydroxides, theformates, the citrates and the dithionates. The acetates and nitrates ofzinc, cadmium, nickel and lead are preferred. In general, it is alsopreferable touse the white or lightly colored salts although for certainspecial purposes the more darkly colored salts can be employed.

One method of providing the print-receiving element with a silverprecipitating layer containing the silver prec1p1tat1ng agent, the saltsfor capturing the sulfide ions and the silica is to form an aqueousdispersion of silica aerogel to which there is added a suitable quantityof one or more of the ion-capturing salts. Thereafter a substantiallylesser molar quantity of a soluble sulfide, such as sodium sulfide, isadded. The anions of sulfide and the cations of the ion-capturing saltcombine to precipitate from the solution relatively insoluble crystalsof the sulfide of the metal of the ion-capturing salt, therebyconverting a portion of the latter to the sulfide. This produces adispersion of the insoluble sulfide in the silica sol while leaving insolution the remainder of the ion-capturing salts. The concentration ofthe latter in the initial solution in relation to the added amount ofthe soluble sulfide is such as to give in the final layer asubstantially greater amount of the ion-capturing salt in proportion tothe sulfide.

In another method of forming the silver precipitating layer the sol ofsilica is first applied as a coating to the print-receiving element andis thereafter impregnated with one or more of the ion-capturing salts byimmersing said coated surface of the element in a solution of said saltsand permitting the same to dry. Thereafter, by dipping the sheet in asoluble sulfide a predetermined portion of the more soluble salt in thesilica layer is converted to give the insoluble sulfide. Some of theion-capturing salt is also dissolved out of the layer during the secondimmersion so that allowance for this loss is made in the quantity of thesoluble salt which is applied in the first immersion. It may also bedesirable to so form the sulfide in the silver precipitating layer thatthere is substantially no excess of the more soluble metallic salts insaid layer and to provide the'more soluble ion-capturing salts inanother layer over or under the silver precipitating layer.

- It will be readily appreciated that the performance of a photographicprocessing, which involves the formation of a positive print by means ofa single liquid application, without recourse to baths of'liquid, is tobe greatly desired where this can be accomplished to give a positiveprint of good pictorial quality from emulsions of high speed as can behad by following the practices described hereinabove. However, becausethe usual developing solution is a highly alkaline solution containing adeveloping agent which rapidly oxidizes in an alkaline environment, itwill also be appreciated that under normal circumstances this type ofliquid processing provides in the print-receiving element a materialwhich, upon exposure to air, tends to form undesirable stains. Unlessthe print is subiected to a thorough Washing, this condition willnormally adversely affect with time the quality of an image formed in aprint-receiving layer. However, as pointed out in my Letters Patent Nos.2,584,030, 2,635,048 and 2,644,756, it is possible to avoid this stainby including in the print-receiving layer a substance whichsubstantially eliminates the stain-forming propensity of thedevelopingsolution in the print-receiving layer.

.It is to be observed that the ion-capturing salts, to which referencehas been made hereinabove, may also serve the function of improving thestability of the positive print provided that they possess, in additionto the aforementioned characteristics, the requisites specified in myabove-mentioned Letters Patent No. 2,584,030. For example, if theion-capturing salt is a salt of a metal which slowly forms insoluble orslightly soluble metallic hydroxides with the hydroxyl ions in thealkaline processing liquid, it will suitably control the alkalinity ofthe print-receiving element to substantially, if not totally,

prevent the formation of undesirable developer stains.

The stabilizing salt should not be a fogging agent and preferably shouldbe white or lightly colored and should give hydroxides which are alsowhite or light in color. It should not decompose in aqueous nonalkalinesolutions. For this purpose, the acetates and nitrates, especially oflead, zinc, nickel and cadmium, are preferred. Of the salts hereinaboveset out asbeing satisfactory for preventing the sulfide ions fromwandering, all exceptthe hydroxide will function satisfactorily asstabilizing agents. In addition, the soluble salts, for example, ofaluminum,

trap the wandering sulfide ions.

may be used to stabilize although they will not serve to .The use of thenovel products of the present invention in the performance of a silverhalide transfer process is processing agent, for example, in a mannerdisclosed in.

my above-mentioned Letters Patent No. 2,647,056, and the processingagent may be one of the film-forming processing agents disclosed in saidpatent. It may comprise, for example, a developing agent such ashydroquinone, an alkali such as sodium hydroxide, a substance, such assodium thiosulfate, for forming a soluble silver complex with unexposedsilver halide, and a high molecular. weight film-forming thickeningagent such as sodium carboxymethyl cellulose. All these materials arepreferably in aqueous solution. These various photographic reagents arepreferably contained in solution in the processingv liquid prior to thespreading thereof as a layer 14, but they maybe in part or wholly addedto the processing liquid as it is spread between elements 10 and 12,said reagents being so located on or adjacent the surface of one or bothof said elements as to be dissolved by or otherwise interacted with theliquid agent when the latter wets said surface.

The liquid processing agent may be provided for spreading as a layer 14between elements 10 and 12 by being contained in an elongated rupturablecontainer 20 which, as shown in Fig. 2, has a length at least equal tothe transverse dimension of the area of photosensitive element 10 towhich the liquid processing agent is to be,

applied. One or more containers 20 may be attached'to one of elements 10and 12 and, in Fig. 2, two such containers are shown secured to theprint-receiving surface of element 12, being spaced apart, lengthwise ofsaid element, a distance equal at least to the length of a single frameof the photo-sensitive element 10. Said elements 10 and 12 may beconnected together so that they can be superposed with the container sopositioned that it can release its contents in a film therebetween. Thecontainer 20 is preferably inexpensive and disposable and so constructedas to be capable of retaining the liquid processing agent or compositiontherein for relatively long periods of time without vapor loss oroxidation. One example of a suitable container of this type is formedfrom a single multilayer sheet of material comprising three laminae. Theinner lamina, which provides the inner surface of the container, isformed of a material which is chemically inert to the reagents in theprocessing agent and which is impervious to the liquid of the agent. Oneclass of materials suitable for this purpose, particularly where theprocessing agent is an alkaline solution, is the polyvinyl acetals, andof the acetals, polyvinyl butyral is a preferred species. A compositioncomprising to 72% by weight of polyvinyl butyral, 10% to 23% by Weightof nitrocellulose, and approximately 5% by weight of dibutyl sebacate issatisfactory as the inner lamina. The intermediate lamina is preferablyimpervious to the vapor of the processing agent and is formed, forexample, of a metallic foil such as lead or silver foil. The outer orbacking lamina is formed of a strong, deformable, relatively inexpensivesheet material such as a kraft paper. 1

The container 20 is preferably formed by taking the single sheet ofthree-ply material and folding the same medially at 22, and thereaftersecuring the end marginal portions 24 and the longitudinal portions 26of the two,

folded faces to one another, providing a central space or cavity 28 forcontaining the processing liquid.

To fill the container it is possible to adhere together the oppositelongitudinally extending marginal'portions 26 and one of the endmarginal portions 24, the container beingd filled through the other endwhich is thereafter seale Photosensitive element 10 may be any of thecommercially available photosensitive silver halide films, the termfilms being understood to include paper-backed emulsions.

I The products of the present invention are particularly useful inimproving the results obtained when:

thetransfer processiiscarried out with one of the highspeedphotosensitive silver halide emulsions such as the' emulsion of therelatively high-speed orthochromatic.

films, e'. g., Eastman Kodak Verichrome film, having an ASA speed ratingof 0200 and an ASA exposure index rating in the daylight of 50, and theextremely high-speed panchromatic emulsions, e.g., Eastman Kodak Super XPan having an ASA speed rating of 0400 and an ASA exposure index ratingin the daylight of 100, and Ansco Triple S Pan.

Element 12 may be formed by applying to a suitable support 12a, forexample, of baryta paper, a coating of a suspension or sol of the silicacontaining the silver precipitating agent. This so] is permitted to dryand provides layer 16. The suspension of silica may be obtained bydispersing the silica, for example, in water, and then adding the silverprecipitating agent either directly or by introducing into the sol saltswhose reaction product is the precipitating agent. The sol may also beapplied to the sheet without the silver precipitating agent, and thesheet with the layer of silica thereon may then be dipped in a solutionor mixture of the silver precipitating agent to deposit the latter insaid layer.

When the foregoing liquid composition is spread or otherwise provided ina layer 14 between elements and '12, the liquid thereof permeates thephotosensitive layer 10b and the developing agent acts to develop thelatent image in said layer. Almost simultaneously with the development,the complex-forming substance, i. e., sodium thiosulfate, forms asoluble silver complex with the undeveloped silver halide, and thesilver complex is transported by the liquid of the processing agent tolayer 16 of element 12. The presence of layer 16 results in a vigorousand relatively concentrated precipitation of the silver from the silvercomplex to form an image of improved density and color, and having moredesirable gamma and contrast characteristics than would be obtained inthe absence of the silica.

Examples of processes for forming a positive image wherein a silverhalide transfer takes place and examples of the novel product of theinvention which is used as the print-receiving element in theperformance of said processes are given below, but it is expresslyunderstood that these examples are merely illustrative and that theinvention is not limited to the materials or proportions set outtherein.

Example 1 A processing agent is prepared which comprises:

' Grams Water 1860 Sodium carboxymethyl cellulose 117 Sodium sulfite 78Sodium hydroxide 74.6 Sodium thiosulfate 14.5 Citric acid 38.5Hydroquinone 52 The processing agent is prepared by dissolving thesodium carboxymethyl cellulose, for example the commercially availableHercules 1362 medium viscosity type, in the water in a mixer at roomtemperature, and the solution is mixed therein for approximately onehour. Thereafter, the sodium sulfite, sodium hydroxide, sodiumthiosulfate and citric acid are added to the solution, the additionbeing effected in an inert atmosphere, for example of nitrogen. Upondissolution of these materials, the hydroquinone is added and thesolution is further mixed for an hour at approximately room temperaturein a nonoxidizing atmosphere of nitrogen.

A print-receiving element 12 provided with a silver prccipitatingstratum16 is prepared by having at least the baryta-coated surface portion of astrip of baryta paper immersed in a mixture comprising the followingingredients:

1% solution of sodium sulfide cc 280 Silica aerogel grams 30 Solutioncontaining 30 g. cadmium acetate, 1 g. neutral lead acetate and 30 g.zinc nitrate dissolved 100 cc. of watere cc 92 to provide a thin coatingof these materials on said surface. As'the baryta paper is removed fromthe bath, the excess mixture'on said surface is removed from the sheetas, 'for example, by the action of a soft buffer'roll'on said sheet asit leaves the bath.

The processing agent is spread in a layer 14 of approximately .002-003in thickness between the coated surface of element 12 and thephotosensitive silver halide emulsion 10b of a photosensitive film 10.Emulsion 10b is a relativcly high-speed orthochromatic emulsion like theemulsion of Eastman Kodak Verichrome film, and has been exposed topredetermined subject matter to form therein a latent image of saidsubject matter, support 10a for said emulsion being a white paper. Thelamination formed by the spreading of the processing agent in a layer i4between elements 10 and 12 is kept intact for approximately one-half toone and one-half minutes, preferably one minute, and at the end of thistime element 12 is stripped from element 10. Element 12, when sostripped, carries a positive print in silver of the subject matter ofthe latent image in emulsion 10b. The sodium carboxymethyl cellulose oflayer 14 adheres to coating 16 of element 12 and solidifies to form afilm thereon. The print obtained in this manner has good color, densityand other pictorial qualities.

Other materials may be substituted for those used in the foregoingprocess and the proportions may be varied to an appreciable extent. Forexample, the film-forming material in the processing agent which impartsthe desired viscosity to the latter may be any of the high molecularweight polymers which are stable to alkalis and which are soluble inaqueous alkaline solutions. For example, such other plastics ashydroxyethyl cellulose, polyvinyl alcohol and the sodium salts ofpolymethacrylic acid and polyacrylic acid may be used. The plastic ispreferably contained in the agent in sufficient quantities to impart tothe composition a viscosity in excess of 1000 centipoises atatemperature of approximately 24 C. Preferably, the viscosity of theprocessing agent is of the order of 1,000 to 200,000 centipoises.

Other developing agents may be used, for example one of the following:p-aminophenol hydrochloride; bromohydroquinone, chlorohydroquinone;diaminophenol hydrochloride; diaminophenol dihydrochloride;toluhydroquinone; monomethyl-p-aminophenol sulfate; a mixture consistingby weight of one-half hydroquinone and onehalfp-hydroxyphenylaminoacetic acid; and a mixture consisting by' weight ofone-fourth hydroquinone and three-fourths p-hydroxyphenylaminoaceticacid.

To form the soluble silver complex, such other complexforming substancesas sodium thiocyanate, ammonium thiocyanate and ammonia may be employed.

Examples of further embodiments of the novel printreceiving elements ofthe present invention and the processes for forming the same are givenbelow:

Example 2 To 24 cc. of a 10% solution of lanthanum chloride there isadded 4 g. of silica aerogel (Santocel C) and 6 cc. of a 1% solution ofsodium sulfide, and these ingredients are thoroughly mixed in amechanical mixer. A layer of the resulting mixture is then applied tothe barytacoated surface of a sheet of baryta paper, and the sheet ispermitted to stand for approximately 15 seconds. Thereafter, the excessof the liquid mixture is removed as by a soft buffer roll from thesurface of the sheet.

Example 3 The process of forming the sheet described in Example 2 may beperformed by substituting for the mixture therein a mixture of thefollowing materials which gives a coating of silica containing palladiumsulfide:

24 cc. of a 10% solution of palladium chloride 4 g. of silica aerogel 4cc. of a 1% solution of sodium sulfide Example 4 The process of formingthe sheet described in Example 2 may be performed by substituting forthe mixture therein a mixture of the following materials which gives acoating of silica containing nickelous sulfide:

40 cc. of a 15% solution of nickelous chloride 7.5 g. of silica aerogel20 cc. of a 1% solution of sodium sulfide Bld 8 ,28 6

96 cc. of a 20% solution of cadmium acetate 15 g. of silica aerogel '30cc. of a 1% solution of sodium sulfide 7.5 g. of silica aerogel 30 cc.of a 1% solution of sodium sulfide Example 7 The process of forming thesheet described in Example '2 may be performed by substituting for themixture therein a mixture of the following materials which gives acoating of silica containing magnesium sulfide:

48 cc. of a 40% solution of magnesium acetate 7.5 g. of silica aerogel18 cc. of a 1% solution of sodium sulfide Example 8 The process offorming the sheet described in Example 2 may be performed bysubstituting for the mixture therein. a mixture of the followingmaterials which gives a coating of silica containing lead selenide:

96cc. of a 40% neutral lead acetate solution 15 g. of silica aerogel 30cc. of a 1% sodium selenide solution Example 9 To 15 grams of Ludox, asolution containing approximately 30% of hydrated colloidal silica inwater, there is added 90 grams of water. Thereafter 24 cc. of a solutionformed by adding 3 grams of sodium sulfide to 46 cc. of water is addedto this suspension, followed by the addition of 12 cc. of a solutionformed by dissolving 2.6 grams of lead acetate in 20 cc. of water.

The resulting mixture is rubbed by hand on the surface of theprint-receiving support. It is preferable to wipe off any excess of themixture from the paper after the rubbing operation.

To obtain different precipitating agents in the silver I precipitatinglayer that is formed according to the process of Example 9, there may besubstituted for the 2.6 grams of lead acetate one of the following saltsin the following quantities:

Grams Zinc acetate 1.42 Cupric acetate 1.34 Manganous acetat 1.60Cadmium acetate 1.92

Example 10 A suspension is formed by mixing 20 grams of silica aerogelin 100 cc. of water. This sol or suspension is then rubbed onto thebaryta-coated surface of a sheet of baryta paper. The sheet is thendried and dipped in a 3% water solution of sodium sulfide for thirtyseconds. The excess liquid is squeegeed from the sheet as it is removedfrom the solution.

Example 11 A suspension is formed by mixing 20 grams of silica aerogelin 100 .cc. of water. This sol or suspension is then rubbed onto thebaryta-coated surface of a sheet of baryta paper. The sheet is thendried and dlpped in a 3% water solution of sodium sulfide for thirtyseconds. The excess liquid is squeegeed from the sheet as it is removedfrom the solution. The sheet is then again dried and dipped for tenseconds in a second solution which is a water solution of neutral leadacetate. The excess liquid is squeegeed from the surface of the sheetand the sheet is dried once more before being used.

Example 12 print-receiving elements 12 of the foregoing Examples 1through 11, said elements may be suitably treated as follows: Thesurface of the element containing the silica stspension is dipped for 30seconds in a solution consisting o 10 grams cadmium acetate 1 gram leadacetate 30 grams zinc acetate cc. of water Excess moisture is removedfrom the sheet as it leaves tbsI soldution, for example with a glassrod, and the sheet is me For the baryta paper of any of the foregoingexamples, there may be substituted a film of plastic such, for example,as polyvinyl alcohol, hydroxyethyl cellulose, sodium carboxymethylcellulose, regenerated cellulose or other self-supporting sheetlikematerials upon which the novel silver precipitating layer'of the presentinvention may be deposited. t

In another form of the product of the present invention, it may bedesirable to provide a coating on the silver precipitating layer 16 of amaterial, such as a plastic, more abrasion resistant than the silica ofthe precipitating layer in order to protect said layer. Thisovercoat ofa plastic material may also serve as a layer which prevents the adhesionof the element 12 of the film-forming material of the layer ofprocessing liquid 14 so that when said element 12 is stripped away fromthe photosensitive film 10 at the completion of the processing, thefilm-forming material remains attached to the photosensitive layer 101).An embodiment of a print-receiving element of this construction is shownin Fig. 3 wherein 12a is the support, 16 is the silver precipitatinglayer, both of which are like layers 12a and 16 of Fig. 1, and there isapplied over layer 16 a thin coating of a film-forming material 18 whichmay be, for example, gum arabic, cellulose acetate-hydrogen phthalate,polyvinyl alcohol, hydroxyethyl cellulose, methyl cellulose, ethylcellulose, cellulose nitrate, sodium alginate, pectin andpolymethacrylic acid. Layer 18 preferably has a thickness of the orderof 1-3 microns, although if it is relatively water permeable itsthickness may be appreciably greater. Layer 18 may contain one or moreof the neutralizing agents which tend to improve the stability of thefinished print.

To provide any of the print-receiving elements 12 of Examples 1 through12 with a protective coating 18 of a more abrasion-resistant plasticwhich may also serve as a layer for minimizing the adhesion between thefilmforming material of layer 14, particularly where. said material issodium carboxymethyl cellulose, said elements 12 of each of saidexamples may be processed as follows:

Example 13 The processed sheet has roll coated thereon against a smoothsurface such, for example, as the polished surface of a metal drum, a 5%aqueous solution of polyvinyl alcohol in a layer whose thickness is ofthe order of .001 inch. An equivalent amount by weight of hydroxyethylcellulose or polymethacrylic acid may be substituted for the polyvinylalcohol of this example.

Example 14 The processed sheet is dipped into a 2% solution of celluloseacetate, the cellulose acetate being dissolved in a mixture of methanol,ethyl acetate and methyl cellosolve, the proportions of said solventsbeing in the ratio of 1:3:3 by volume, respectively. The dipped barytapaper is removed from the solution in a vertical position to permit theexcess liquid to drip off, a sufficient quantity of the solutionremaining on the surface of the paper to provide the latter with acoating of cellulose acetate of the desired thickness.

Example 15 A 10% solution of celluloseacetate-hydrogen phthalate inacetone is roll coated on the processed sheet in a thickness ofapproximately .001 inch.

In a similar manner, such other materials as methyl cellulose, cellulosenitrate, sodium alginate, ethyl cellulose, gum arabic and pectin may beapplied as layer 18 to the-processed sheet. It is, of course, understoodthat suitable solvents for the materials are employed, said solventsbeing preferably water for such materials as are readily water soluble,and may be toluene for ethyl cellulose anda mixture of methanol andethyl acetate for cellulose nitrate.

'11 Although the silver precipitating layer of the present invention isconstituted primarily of the silica, it may containtherein a smallquantity, preferably not exceeding 10% by weight of the silica, of afilm-forming substance such as gum arabic, hydroxyethyl cellulose or anyExample 16 The following ingredients are mixed in the order named: Watercc 595 Gum arabic cc 3.5 Cadmium acetate grams 22.76 Silica aerogel do36 Sodium selenide do 10 A sheet of baryta is dipped in the mixture,withdrawn, and the excess liquid squeegeed. therefrom.

Other plastics may be substituted for the gum arabic. Also, bysubstituting salts of other metals for the cadmium acetate differentmetallic selenides may be obtained in the sol.

Another class of compounds especially useful in controlling thealkalinity of the print-receiving element after the formation of thepositive print therein is the organic compounds which react in alkalinesolution to consume alkali, as disclosed in my above-noted LettersPatent No. 2,635,048. Preferred from this class are the esters(including lactones), the anhydrides, the alpha-halohydrins and thealdehydes which have a specific rate of alkaline hydrolysis at 25 C.greater than 80 liters per mol per minute and, from this class, thepreferred species are compounds which do not volatilize too rapidly, i.e., compounds whose boiling points are in excess of 150 C.

Examples of preferred species of these compounds are: diethyl oxalate,ethyl oxamate, diethyl d-tartrate, a hydroxybenzaldehyde, dimethyldiacetyltartrate, dimethyl fumarate, dimethyl malate, dimethyl oxalate,dimethyl tartrate, polyethylene oxalate, benzoic anhydride, di-nbutyloxalate, n-butyl oxamate, di-n-butyl tartrate, trismethyl citrate, ethylcyanoacetate, ethyl N-B hydroxyethyl oxam'a'te, glucono delta lactone,'glyceryl trimethyl oxalate and cellulose methyl oxalate,di-B-hydroxyethyl malonate, hydroxyethyl lactate, diethyl malate,diethyl tartrate, di-B-hydroxycthyl malate, ethyl acetoacetate, di-

butyl malate, butyl lactate, diethyl malonate, glyceryl chlorohydrin,and di-B-hydroxyethyl succinate.

The positive print is subject to severalsources of instability whichstem, for example, from the oxidation of the developer in thehighlights, the discoloration of some of the unexhausted chemicalcomponents in the positive prints by exposure to visible and nearvisible radiation,

and the partial bleaching of the silver.

It has been determined that these effects are most nearly eliminated bycombining the stabilizing effects of the soluble metallic salts and theorganic alkali-consuming compounds, i. e., by using at least one of eachof these classes of stabilizers in the print-receiving element.

Examples of suitable print-receiving elements which embody thiscombination of stabilizers, together with the novel silver precipitatinglayer of the invention, are the following:

Example 17 The baryta-coated surface of a sheet of baryta paper isimmersed in a mixture consisting of Water cc 1000 Arabol '-cc 150Dimethyl d-tartrate grams 400 Lead acetate do 70 Cadmium, acetate do 50Zinc acetate do 40 The sheet is then dried and there is applied over theforegoing coating a further coating consisting of:

Silica aerogel grams 300 1% aqueous solution sodium sulfide cc 2800Cadmium acetate grams 30 Lead acetate do 1 Zinc nitrate do 30 Water,-.-c

Example I 8 The baryta-coated surface of a sheet of baryta paper isdipped in a solution consisting of:

Ethanol cc 1000 Zinc nitrate grams 120 Ethyl oxamate do The treatedsurface of this sheet is then provided with a sulfide-containing coatingconsisting of the following:

It is to be noted from the foregoing examples that the silverprecipitating agent is present in the sheet in a very small amount.Concentrations, for example, as low as 2X10" to 2 l0- gram-moles foreach square foot of the surface area of the print-receiving element haveproven adequate.

Although in the foregoing, submacroscopic particles of silica,preferably colloidal in size, are disclosed as preferred for the matrixof the silver precipitating layer, other materials may be usefullyemployed for this purpose such, for example, as those disclosed in mycopending application Serial No. 727,385, including bentonite andfullers earth. In general, therefore, it is to be understood that thematrix material of the silver precipitating :layer may compriseparticles of a waterinsoluble, preferably inorganic. chemically inert,adsorbent material which has a relatively low ccetficient adsorption forlight as compared to silver and which gives a matrix which issubstantially free of protective colloid action for silver.

Since certain changes may be made in the above product and processwithout departing from the scope of the invention herein involved, it isintended that all matter contained in the above description or shown inthe accompanying drawing shall be interpreted as illustrative and not ina limiting sense.

What is claimed is:

l. A photographic product comprising a photosensitive element includinga silver halide layer, a base layer, and a rupturable containing meansholding a liquid including water, said base layer having adjacent onesurface thereof a dispersion of a silver precipitating agent from theclass consisting of the metal sulfides and selenides which aresubstantially insoluble in said liquid and a dispersion of at least onemetallic salt which is at least moderately soluble and'substantiallyirreducible in said liquid, the last-named salt having as its cation ametal which forms, with the anion of the silver precipitating agent, asalt which is substantially insoluble in said liquid and which gives upits anions to silver ions by displacement, said product'havingpositioned therein'photographic reagents, including a silver halidedeveloper and a silver halide solvent, said containing means and saidlayers being so held together that said containing means is capable,upon rupture, of releasing at least a part of its contents to permeatesuperposed portions of said silver halide layer and said base layer,said liquid, upon release, rendering said silver halide developer andsaid silver halide solvent effective to develop a latent image in saidsilver halide layer and to form soluble silver complex with theundeveloped silver halide of said silver halide layer, said liquid, uponrelease, additionally transporting said soluble silver complex in tl1edirection of said silver precipitating agent wherein part at least ofthe soluble silver complex is reduced to silver to produce the positiveprint.

2. The product of claim 1 wherein said base layer comprises colloidalparticles of silica and said silver precilpitating agent is dispersedamong saidparticles of $1 ma.

3. The product of claim 1 wherein said base layer comprises a matrix ofa water-insoluble, inorganic, relatively inert, adsorbent substance andsaid silver precipitating agent is dispersed in said matrix.

4. The product of claim 3 wherein said moderately soluble salt is fromthe class consisting of the nitrates and acetates of cadmium, zinc andlead.

5. A photographic product comprising a silver halide layer, a'baselayer, and a rupturable container holding a liquid includingwater, saidlayers and said container being attached together so as to permit s'aidlayers to be superposed with said container so positioned as to releaseits liquid for spreading in a film between said layers, the liquid insaid container comprising a silver halide developer, a silver halidesolvent and a thickening agent, said base layer having adjacent onesurface thereof a dispersion of a silver precipitating agent from theclass consisting of the metal sulfides and selenides which aresubstantially insoluble in said liquid and a dispersion of at least onemetallic salt which is at least moderately soluble and substantiallyirreducible in said liquid, the last-named salt having as its cation ametal which forms, with the anion of said silver precipitating agent, asalt which is substantially insoluble in said liquid and which gives upits anions to silver ions by displacement.

6. The product of claim wherein said base layer comprises submacroscopicparticles of silica and said silver precipitating agent is aggregatedamong said particles of silica.

7. The product of claim 5 wherein said base layer comprises a matrix ofa water-insoluble, inorganic, relatively inert, adsorbent substance andsaid silver precipitating agent is dispersed in said matrix.

8. The product of claim 7 wherein said moderately soluble salt is fromthe class consisting of the nitrates and acetates of cadmium, zinc andlead.

9. A photographic product capable of forming transfer prints inconjunction with a photosensitive silver halide element, said productcomprising a rupturable containing means, holding an aqueous liquid, anda sheet support upon which said containing means is mounted, said sheetsupport providing an image-receiving area adjacent said containing meansonto which said liquid is spreadable in a thin layer directly from saidcontaining means, said product carrying a silver halide developer and asilver halide solvent, said sheet support having, adjacent the surfacemounting said containing means and at least coextensive with saidimage-receiving area, a dispersion of a silver precipitating agent fromthe class consisting of the metal sulfides and selenides which aresubstantially insoluble in said liquid and a dispersion of at least onemetallic salt which is at least moderately soluble and substantiallyirreducible in said liquid, the last-named salt having as its cation ametal which forms, with the anion of the silver precipitating agent, asalt which is substantially insoluble in said liquid and which gives upits anions to silver ions by displacement, said silver halide developer,said silver halide solvent, said liquid and said salts being sufficientin amount and being so located, in relation to said image-receivingarea, that the spreading of said liquid over said area disperses silverhalide developer and silver halide solvent throughout said area inadequate quantity to form a transfer print of a latent image in an areaof a contiguous silver halide element equivalent to said image-receivingarea.

10. The product of claim 9 wherein said support comprises a matrix ofsubmacroscopic particles of silica and said silver precipitating agentis dispersed among said particles of silica.

11. The product of claim 9 wherein said. support comprises a matrix of awater-insoluble, inorganic, relatively inert, adsorbent substance andsaid silver precipitating agent is dispersed in said matrix.

12. The product of claim 11 wherein said moderately soluble salt is fromthe class consisting of the nitrates and acetates of cadmium, zinc andlead.

13. A photographic product capable of forming transfer prints inconjunction with a photosensitive, silver halide element, said productcomprising a rupturable container holding an alkaline aqueous solutionof a silver halide developer, a silver halide solvent and a film-formingplastic, and a sheet support upon which said container is mounted, saidsheet support providing an image-receiving area adjacent said containingmeans onto which said liquid solution is spreadable in a thin layerdirectly from said container, said sheet support having, adjacent thesurface mounting said container and at least coextensive with saidimage-receiving area, a dispersion of a silver precipitating agent fromthe class consisting of the metal sulfides and selenides which aresubstantially insoluble in said solution and a dispersion of at leastone metallic salt which is at least moderately soluble in said solution,the last-named salt having as its cation a metal which forms asubstantially insoluble and relatively irreducible salt with the anionof the silver precipitating agent, said silver halide developer, saidsilver halide solvent, said liquid and said salts being sufiicient inamount and being so located, in relation to said image-receiving area,that the spreading of said solution over said area disperses silverhalide developer and silver halide solvent throughout said area inadequate quantity to form a transfer print of a latent image in an areaof a contiguous silver halide element equivalent to said image-receivingarea.

14. The product of claim 13 wherein said support comprises colloidalparticles of silica and said silver prlecipitating agent is dispersedamong said particles of $1 ica.

15. The product of claim 13 wherein said support comprises a matrix of awater-insoluble, inorganic, relatively inert, adsorbent substance andsaid silver precipitating agent is dispersed in said matrix.

16. The product of claim 15 wherein said moderately soluble salt is fromthe class consisting of the nitrates and acetates of cadmium, zinc andlead.

17. The process of forming positive images in silver which comprisesdeveloping a latent negative image in a silver halide emulsion layer,forming an imagewise distribution of soluble silver complex with theundeveloped silver halide of said emulsion layer, transferring insolution from said emulsion layer at least part of said imagewisedistribution of said soluble silver complex to an image-carrying layerso superposed adjacent said emulsion layer as to receive a depthwisediffusion of said complex from said emulsion layer without appreciablydisturbing said imagewise distribution, reducing to silver the silverions of said soluble silver complex in a stratum of said image-carryinglayer which contains a dispersion of a silver precipitating agent fromthe class consisting of the sulfides and selenides which aresubstantially insoluble in said solution and at least one metallic saltwhich is at least moderately soluble and substantially irreducible insaid solution, the last-named salt having as its cation a metal whichforms, with the anion of the silver precipitating agent, a salt which issubstantially insoluble in said solution and which gives up its anionsto silver ions by displacement, the reduction of said silver forming animage in silver in said image-carrying layer which is a positive of thesubject matter of said latent image.

18. The process of claim 17 wherein the silver precipitating agent isdispersed in a matrix comprising colloidal particles of silica and thepositive silver image is formed in said matrix.

19. The process of claim 17 wherein the silver precipitating agent isdispersed among particles of a waterinsoluble, relatively inert,inorganic, adsorbent substance.

20. The process of claim 17 wherein said moderately soluble salt is fromthe class consisting of the nitrates and acetates of cadmium, zinc andlead.

21. A photographic product comprising a photosensitive element whichincludes a silver halide layer, a printreceiving element for receivingby transfer a positive print, and a rupturable containing means holdinga liquid, said product having positioned therein photographic reagentsincluding a silver halide developer and a silver halide solvent, saidcontaining means and said elements being so held together that saidcontaining means is capable, upon rupture, of releasing at least part ofits contents to permeate superposed portions of said elements includingsaid silver halide layer, the portion of said printreceiving elementadapted to be permeated by said liquid including a mixture of salts, atleast one of said salts being a silver precipitation initiator from theclass consisting of metallic sulfides and selenides and at least oneother of said salts being from the class consisting of the nitrates andacetates of cadmium, zinc and lead, said liquid, upon release, renderingsaid silver halide developer and said silver halide solvent effective todevelop a latent negative image in said silver halide layer and to formsoluble silver complexes with the undeveloped silver halide in saidsilver halide layer, said salts initiating and so controlling theprecipitation of the silver from said soluble silver complex as to forma transfer image in silver adjacent the surface of the print-receivingelement, said image having improved color and density characteristics.

22. A photographic product capable of forming transfer prints inconjunction with a silver halide element, said product comprising arupturable containing means holding a liquid, and a sheet support uponwhich said containing means is mounted, said sheet support providing animage-receiving area adjacent said containing means onto which saidliquid is spreadable in a thin layer drrectly from said containingmeans, said product carrying a silver halide developer and a silverhalide solvent, said image-receiving area of said support including amixture of salts, at least one of said salts being a silverprecipitation initiator from the class consisting of metallic sulfidesand selenides and at least one other of said salts being from the classconsisting of the nitrates and acetates of cadmium, zinc and lead, saidliquid and said other reagents being suflicient in amount and beingrendered effective by the spreading of said liquid on the imagereceivingarea to form a transfer print on said imagereceiving area of a latentimage contained in an area of a silver halide element equivalent to saidimage-receiving area.

23. A photographic product capable of forming transfer prints inconjunction with a photosensitive silver halide element, said productcomprising a rupturable containing means holding an alkaline liquidsolution of a silver halide developer, a silver halide solvent and anorganic filmforming colloid, and a sheet support upon which saidcontaining means is mounted, said sheet support providing animage-receiving area adjacent said containing means onto which saidliquid solution is spreadable in a thin layer directly from saidcontaining means, said support having distributed, at least throughoutsaid imagereceiving area, a mixture of salts, at least one of said saltsbeing a silver precipitation initiator from the class consisting ofmetallic sulfides and selenides and at least one other of said saltsbeing from the class consisting of the nitrates and acetates of cadmium,zinc and lead, said solution and said salts being sufiicient in amountso that the spreading of said liquid over said area provides reagentsthroughout said area in adequate quantity to form a transfer print of alatent image in an equivalent area of a silver halide element.

24. A print-receiving element for having transfer prints formed thereonby precipitating the silver of an imagewise distribution of a solublesilver complex brought into contact therewith, said element having atleast one surface portion thereof permeable to an aqueous solution of asoluble silver complex, said surface portion having therein a dispersionof at least one silver precipitating agent from the class consisting ofthe metal sultides and selenides which are substantially water-insolubleand a dispersion of at least one metallic salt which is at leastmoderately soluble and substantially irreducible in an aqueous solutionof a silver halide developer, the lastnamed salt being present in asubstantially greater concentration than said precipitating agent andhaving as its cation a metal which forms, with the anion of the silverprecipitating agent, a salt which is substantially insoluble in anaqueous solution and which, in said solution, gives up its anions tosilver ions by displacement.

25. The print-receiving element of claim 24 wherein the said solublesalt is at least one salt from the class conill '16 sistng of thenitrates and acetates of cadmium, zinc and lea 26. The product of claim24 wherein said element includes a sheetlike support for said surfaceportion and said surface portion includes a thin, macroscopicallycontinuous, silver precipitating layer comprising particles of awater-insoluble, relatively inert, inorganic, adsorbent substance.

27. The product of claim 24 wherein said permeable surface portioncomprises a macroscopically continuous stratum of submacroscopicparticles of silica and said silver precipitating agent is dispersed insaid stratum.

28. The product of claim 24 wherein the element includes a sheet ofpaper as a support for said surface portion.

29. The product of claim 24 wherein said element includes a sheet ofplastic as a support for said surface portion.

30. A print-receiving element for having transfer prints formed thereonby precipitating the silver of a soluble silver complex brought intocontact therewith, said element being very thin in relation to itslength and breadth and having at least one surface portion thereofpermeaable to a solution of a soluble silver complex, said surfaceportion having therein a dispersion of at least one silver precipitatingagent from the class consisting of the metallic sulfides and selenideswhich are substantially water-insoluble and a dispersion of at least onemetallic salt which is at least moderately soluble and substantiallyirreducible in an aqueous solution of a silver halide developer, thelast-named salt being present in a substantially greater concentrationthan said precipitating agent and having at its cation a metal whichforms with the anion of the silver precipitating agent a salt which issubstantially insoluble in an aqueous solution and which in saidsolution gives up its anions to silver ions by displacement, saidsurface portion having a low optical density against which an image insilver is readily 'visible.

31. The product of claim 30 wherein said element includes a sheet ofbaryta paper as a support for said surface portion.

32. The product of claim 30 wherein said element includes a sheet ofplastic as a support for said surface portion.

33. The product of claim 30 wherein said element includes a sheetlikesupport for said surface portion and said surface portion includes athin, macroscopically continuous, silver precipitating layer comprisingparticles of a water-insoluble, relatively inert, inorganic, adsorbentsubstance.

34. The print-receiving element of claim 33 wherein the said solublesalt is at least one salt from the class consisting of the nitrates andacetates of cadmium, zinc and lead.

No references cited.

1. A PHOTOGRAPHIC PRODUCT COMPRISING A PHOTOSENSITIVE ELEMENT INCLUDINGA SILVER HALIDE LAYER, A BASE LAYER, AND A REPTURABLE CONTAINING MEANSHOLDING A LIQUID INCLUDING WATER, SAID BASE LAYER HAVING ADJACENT ONESURFACE THEREOF A DISPERSION OF A SILVER PRECIPITATING AGENT FROM THECLASS CONSISTING OF THE METAL SULFIDES AND SELENIDES WHICH ARESUBSTANTIALLY INSOLUBLE IN SAID LIQUID AND A DISPRESION OF AT LEAST ONEMETALLIC SALT WHICH IS AT LEAST MODERATELY SOLUBLE AND SUBSTANTIALLYIRREDUCIBLE IN SAID LIQUID, THE LAST-NAMED SALT HAVING AS ITS CATION AMETAL WHICH FORMS, WITH THE ANION OF THE SILVER PRECIPITATING AGENT, ASALT WHICH IS SUBSTANTIALLY INSOLUBLE IN SAID LIQUID AND WHICH GIVES ISUP ITS ANIONS TO SILVER IONS BY DISPLACEMENT SAID PRODUCT HAVINGPOSITIONED THEREIN PHOTOGRAPHIC REAGENTS, INCLUDING A SILVER HALIDEDEVELOPER AND A SILVER HALIDE SOLVENT, SAID CONTAINING MEANS AND SAIDLAYERS BEING SO HELD TOGETHER THAT SAID CONTAINING MEANS IS CAPABLE,UPON RUPTURE, OF RELEASING AT LEAST A PART OF ITS CONTENTS TO PERMEATESUPERPOSED POTIONS OF SAID SILVER HALIDE LAYER AND SAID BASE LAYER, SAIDLIQUID, UPON RELEASE, RENDERING SAID SILVER HALIDE DEVELOPER AND SAIDSILVER HALIDE SOLVENT EFFECTIVE TO DEVELOP A LATENT IMAGE IN SAID SILVERHALIDE LAYER AND TO FROM SOLUBLE SILVER COMPLEX WITH THE UNDEVELOPEDSILVER HALIDE OF SAID SILVER HALIDE LAYER, SAID LIQUID, UPON RELEASE,ADDITIONALLY TRANSPORTING SAID SOLUBLE SILVER COMPLEX IN THE DIRECTIONOF SAID SILVER PRECIPITATING AGENT WHEREIN PART AT LEAST OF THE SOLUBLESILVER COMPLEX IS REDUCED TO SILVER TO PRODUCE THE POSITIVE PRINT.